Effect of Plant Growth Promoting Rhizobacteria (PGPRs) and Chemical Fertilizer Application on Solanum tuberosum L. Cultivars in Aeroponic Culture System and Field Conditions

Optimization of mineral nutrition in aeroponic systems is one of the most significant factors in producing high-quality and high yields of healthy seed tubers in potato ( Solanum tuberosum L.). The present study was conducted at the Research Farm and Greenhouse of Agricultural and Natural Resources Center of Ardabil during two successive years (2018-2019). For the aeroponic system an experiment was set up as factorial based on completely randomized design with three replicates. There were three experimental treatments viz: seedlings of three potato cultivars (Agria, Caeser, and Banba), chemical fertilizer (fertilizer application and no fertilizer application), and three bacterial combined inoculants (without inoculation as control, Pseudomonas putida 169, Azospirillum lipoferum OF, and Azetobacter chroococcum 5). In the second year, a trial was set up under field conditions as factorial based on RCBD (completely randomized block design) using two factors in three replications. These factors included mini-tubers of potato cultivars (Agria, Caeser and Banba) produced in aeroponic culture and PGPRs (without PGPRs and PGPRs inoculation including Pseudomonas putida , Azospirillum lipoferum , and Azetobacter chroococcum ). Results of the aeroponic culture revealed that the largest and highest mini-tuber numbers was produced by cv. Banba and the greatest number of stolons and number of days to tuber set belonged to cv. Caeser due to nutrition by chemical fertilizer. Compared with fertilization treatment, combined bacterial inoculation increased the plant height. Among the cultivars tested, plants of Caeser was significantly taller. The highest number of stolon was produced in cv. Banba. Regarding the field experiment results, inoculation of cv. Agria and Banba with A. lipoferum caused a drastic increase in tuber numbers, and inoculation with P. putida resulted in significant increases in tuber numbers in cv. Banba. Agria and Caeser produced the largest tubers when were inoculated with A. lipoferum and the greatest tuber dry weight for Agria was obtained when was inoculated with A. lipoferum. Caeser had the highest mean number of branches among cultivars. Based on these findings, chemical fertilizers application in aeroponic cultivation and treating with A. lipoferum in the field-grown plants may improve potato yield.